This current study consists of two phases. In the first step, PbS, Sb2S3:Co(0.25%), Sb2S3:Co(0.5%), Sb2S3:Co(0.75%) and Sb2S3:Co (1%) and Sb2S3:Co (2.5%) thin films were successfully synthesized on Zn2SnO4 coated on FTO conductive glasses using chemical bath deposition method at room temperature. The photovoltaic properties of the synthesized thin films were examined by applying both incident photon-to-current efficiency (IPCE) and current density (J)-voltage (V) measurements. It was observed that Co:Sb2S3 thin films with different Co concentrations have higher IPCE (%) and power conversion efficiency (eta%) values higher than pure Sb2S3. Moreover, the Co concentration, which provides the best efficiency, was determined as 1% compared to other concentrations. In the second phase of the study; structural, elemental and optical properties of Sb2S3:Co (1%) thin film were investigated using X-ray diffraction, energy dispersive X-ray and optical absorption measurements, respectively. Consequently, it was clearly observed that the Co dopant affects particle size, energy band gap and power conversion efficiency of Sb2S3 thin films. In addition, our study suggests that Co:Sb2S3 thin films are promising materials that can be used in photovoltaic applications.